CN111801130B

CN111801130B - Humidifier starting method and system adopting same

Info

Publication number: CN111801130B
Application number: CN201880090457.2A
Authority: CN
Inventors: C·J·麦克拉肯
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2017-12-29
Filing date: 2018-12-26
Publication date: 2023-09-12
Anticipated expiration: 2038-12-26
Also published as: JP7028980B2; EP3731915A1; US20190201651A1; EP3731915B1; US20220170454A1; CN111801130A; WO2019129779A1; US20220170453A1; JP2021508545A

Abstract

A method for operating a humidifier (20) coupled to a gas flow generator. The humidifier has a pump (24) for providing a supply of water (20) to a heating plate (28). The method comprises the following steps: providing power to the gas flow generator; raising the temperature of the heating plate from ambient temperature to about a first predetermined temperature; powering the pump at about a predetermined first duty cycle; monitoring the temperature of the heating plate until one of: a drop in temperature is detected, or a predetermined period of time has elapsed; one of the following: if a decrease in the temperature is detected, the duty cycle of the pump is increased, or if the predetermined period of time has elapsed, the pump is turned off.

Description

Humidifier starting method and system adopting same

Technical Field

The present invention relates to humidifiers for use in airway pressure support systems for delivering a flow of humidified gas to the airway of a patient, and more particularly to a method of starting up such humidifiers.

Background

Many people suffer from respiratory disturbances during sleep. Sleep apnea is a common example of such sleep apnea suffered by millions of people worldwide. One type of sleep apnea is Obstructive Sleep Apnea (OSA), a condition in which the sleep is repeatedly interrupted due to obstruction of the airway, typically the upper airway or pharyngeal region, without breathing. It is generally believed that obstruction of the airway is due, at least in part, to the general relaxation of the muscles that stabilize the upper airway segment, thereby causing the tissue to collapse the airway. Another type of sleep apnea syndrome is central apnea, which is the cessation of breathing due to the absence of respiratory signals from the brain respiratory center. An apneic condition, whether obstructive, central, or a combination of obstructive and central, is defined as a complete or near cessation of breathing, e.g., a 90% or more reduction in peak respiratory gas flow.

Those suffering from sleep apnea experience sleep fragmentation and complete or near complete cessation of ventilation intermittently during sleep, with severe levels of oxyhemoglobin desaturation possibly occurring. These symptoms may translate clinically into extreme daytime sleepiness, cardiac arrhythmias, pulmonary hypertension, congestive heart failure, and/or cognitive dysfunction. Other consequences of sleep apnea include right ventricular dysfunction, carbon dioxide retention during wakefulness and sleep, and continuously reduced arterial oxygen tension. Sleep apnea patients may be at risk of excessive mortality due to these factors, as well as an increased risk of accidents while driving and/or operating potentially dangerous equipment.

Even if the patient does not suffer from a complete or nearly complete airway obstruction, adverse effects, such as arousal from sleep, are known to occur with only partial airway obstruction. Partial obstruction of the airway often results in shallow breathing known as hypopneas. Hypopneas are generally defined as a 50% or more reduction in peak respiratory gas flow. Other types of sleep disordered breathing include, but are not limited to: upper Airway Resistance Syndrome (UARS) and airway oscillations, such as pharyngeal wall oscillations, often referred to as snoring.

It is known to treat sleep disordered breathing by applying Continuous Positive Airway Pressure (CPAP) to the airway of a patient. This positive pressure effectively "splints" the airway, thereby maintaining an open path to the lungs. It is also known to provide a positive pressure therapy in which the pressure of the gas delivered to the patient varies with the patient's respiratory cycle, or with the patient's respiratory effort, to increase patient comfort. This pressure support technique is known as bi-level pressure support, in which the Inspiratory Positive Airway Pressure (IPAP) delivered to the patient is higher than the Expiratory Positive Airway Pressure (EPAP). It is also known to provide a positive pressure therapy in which the pressure is automatically adjusted based on a detected patient condition, such as whether the patient is experiencing an apnea and/or hypopnea. This pressure support technique is referred to as auto-titration pressure support because the pressure support device attempts to provide the patient with a pressure that is only as high as is required to treat the respiratory disorder.

The pressure support therapy just described involves placing a patient interface device on the face of a patient that includes a mask component having a soft, flexible seal. The mask component may be, but is not limited to: a nasal mask covering the nose of a patient, a nasal/oral mask covering the nose and mouth of a patient, or a full face mask covering the face of a patient. Such patient interface devices may also employ other patient contacting components, such as forehead supports, cheek pads, and chin pads. The patient interface device is typically secured to the patient's head by a headgear assembly. The patient interface device is connected to the gas delivery tube or conduit and interfaces the pressure support apparatus with the airway of the patient so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.

Humidifiers are often provided between or integral with the PAP machine and the user interface in order to humidify the otherwise relatively dry compressed air generated by the PAP machine. Generally, humidifiers can be classified as heating type or passing type.

The heated humidifier has an internal heater that increases the temperature of the air being carried between the CPAP machine and the mask. Inhalation of cool air can be uncomfortable and cause sore throat. Most machines on the market today use heated humidifiers, as they tend to provide comfortable breathing conditions.

Pass-through humidifiers are so named because the air literally "passes" through the water in the humidifier on its way from the machine to the mask. It wicks moisture and, like a heated humidifier, makes air breathe easier and less irritating to the throat.

In WO2016/036260A1, a respiratory humidification system for providing humidification of a gas passing through a gas passage prior to being provided to the airway of a patient is disclosed. The respiratory humidification system includes a liquid flow controller that provides a controlled flow of liquid, a heating system including a heating surface configured to be positioned in a gas pathway and provide humidification of gas passing through the pathway, wherein the heating system receives the controlled flow of liquid, and one or more hardware processors that provide deterministic control of a humidity level of the gas passing through the gas pathway by commanding the liquid flow controller to regulate the controlled flow of liquid received at the heating system.

In US2017/028159A1, a system for delivering gas to a patient during a medical procedure is provided. The system comprises a heater arranged to heat at least one of the gas and the humidification liquid, a controller arranged to control the system according to a first mode during delivery of the first gas flow rate and a second mode during delivery of the second gas flow rate. The controller monitors electrical characteristics of the heater to select an operating mode and/or to determine an operating state of the system.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved humidifier and an airway pressure support system including the humidifier.

As one aspect of the disclosed concept, a method for operating a humidifier coupled to a gas flow generator is provided. The humidifier has a pump for providing a supply of water to a heating plate, the method comprising: providing power to the gas flow generator; raising the temperature of the heating plate from ambient temperature to about a first predetermined temperature; powering the pump at about a predetermined first duty cycle; monitoring the temperature of the heating plate until one of: a drop in temperature is detected, or a predetermined period of time has elapsed; one of the following: if a decrease in the temperature is detected, the duty cycle of the pump is increased, or if the predetermined period of time has elapsed, the pump is turned off.

The method may further include waiting a first predetermined period of time after powering the gas flow generator and before raising the temperature of the heating plate to about the first predetermined temperature.

The first predetermined period of time may be about 10 seconds.

The first predetermined temperature may be about 50 ℃.

The method may further include receiving an indication to power the system and, in response thereto, providing power to the pressure generating device.

The method may further include waiting a second predetermined period of time after increasing the temperature of the heating plate to about the first predetermined temperature and before powering the pump at about the predetermined first duty cycle.

The second predetermined period of time may be about 10 seconds.

The predetermined first duty cycle may be a duty cycle of about 20%.

The method may further include, after increasing the duty cycle of the pump, increasing the temperature of the heating plate to about a second predetermined temperature.

The second predetermined temperature may be about 120 ℃.

As another aspect of the invention, a processing unit is provided for use in a pressure support system having a gas flow generator and a humidifier for delivering a humidified gas flow to an airway of a patient. The humidifier has a pump for providing a water supply to the heating plate. The processing unit is programmed to: providing power to the gas flow generator; raising the temperature of the heating plate from ambient temperature to about a first predetermined temperature; powering the pump at about a predetermined first duty cycle; monitoring the temperature of the heating plate until one of: a drop in temperature is detected, or a predetermined period of time has elapsed; one of the following: if a decrease in the temperature is detected, the duty cycle of the pump is increased, or if the predetermined period of time has elapsed, the pump is turned off.

The processing unit may be further programmed to wait a first predetermined period of time after powering the gas flow generator and before raising the temperature of the heating plate to about the first predetermined temperature.

The first predetermined period of time may be about 10 seconds.

The first predetermined temperature may be about 50 ℃.

The processing unit may be further programmed to receive an indication to power the system and in response thereto provide power to the pressure generating device.

The processing unit may be further programmed to wait a second predetermined period of time after raising the temperature of the heating plate to about the first predetermined temperature and before powering the pump at about the predetermined first duty cycle.

The second predetermined period of time may be about 10 seconds.

The predetermined first duty cycle may be a duty cycle of about 20%.

The processing unit may be further programmed to increase the temperature of the heating plate to about a second predetermined temperature after increasing the duty cycle of the pump.

The second predetermined temperature may be about 120 ℃.

These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings. All of which form part of the present specification wherein like reference numerals designate corresponding parts throughout the several views. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

Drawings

FIG. 1 is a schematic diagram of an airway pressure support system according to one particular non-limiting embodiment, in which the present invention may be implemented in various embodiments thereof, shown with its patient interface device disposed on a patient's face;

fig. 2 is a schematic diagram of a humidifier according to one specific non-limiting embodiment of the invention, in which various other example embodiments of the invention may be implemented;

FIG. 3 is a partial schematic cross-sectional view of another airway pressure support system and humidifier for use with the system, taken along a plane lying on the longitudinal axis of the gas flow path through the humidifier according to one specific non-limiting embodiment of the invention;

FIG. 4 is a cross-sectional view of the humidifier of FIG. 3 taken along a plane perpendicular to the longitudinal axis of the gas flow path through the humidifier;

FIG. 5 is a partial schematic cross-sectional view of another airway pressure support system and humidifier for use with the system, taken along a plane lying on the longitudinal axis of the gas flow path through the humidifier according to one specific non-limiting embodiment of the invention;

Fig. 6 is a simplified cross-sectional view of the humidifier portion of Fig. 5 obtained along lines A-A of Fig. 5;

Fig. 7 is a simplified cross-sectional view of a portion of another humidifier according to one specific non-limiting embodiment of the invention;

FIG. 8 is a schematic diagram of another airway pressure support system and humidifier for the system, wherein the invention may be implemented in various embodiments thereof, according to one specific non-limiting embodiment;

FIGS. 9 and 10 are isometric and front views, respectively, of the airway pressure support system of FIG. 8 and a water chamber and filter for the system, shown with the water chamber in a first position;

FIGS. 11A and 11B are cross-sectional views of the airway pressure support system of FIG. 8 and a water chamber and filter for the system, shown with the water chamber in a first position and a second position, respectively;

FIG. 12 is an exploded isometric view of the water chamber and filter of FIGS. 9-11;

FIGS. 13 and 14 are front and isometric views, respectively, of the water chamber and filter of FIG. 12, shown collapsing the water chamber to a second position;

fig. 15 is a schematic diagram of a portion of another humidifier for an airway pressure support system according to one particular non-limiting embodiment, wherein the present invention may be implemented in various embodiments thereof;

fig. 16 is a simplified top plan view of a portion of the humidifier of fig. 15;

FIG. 17 is another schematic view of a portion of the humidifier of FIG. 15, shown rotated by a maximum operating angle;

FIG. 18 is a schematic diagram of a gas flow generator and humidifier of an airway pressure support system according to one specific non-limiting embodiment of the invention;

fig. 19 is a flow chart of a method for activating a humidifier according to one specific non-limiting embodiment of the invention;

FIG. 20 is a schematic cross-sectional view of an example pump according to a specific non-limiting embodiment of the invention;

FIG. 21 is an exemplary wiring schematic for a pump according to one specific non-limiting embodiment of the invention; and is also provided with

FIG. 22 is an exemplary power delivery profile for operating a solenoid pump according to one specific non-limiting embodiment of the invention.

Detailed Description

As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, a statement that two or more parts or components are "coupled" shall mean that the parts are connected together or operate together, either directly or indirectly (i.e., through one or more intermediate parts or components), so long as linking occurs. As used herein, "directly coupled" means that two elements are in direct contact with each other. As used herein, "fixedly coupled" or "fixed" refers to two components being coupled to move as one object while maintaining a constant orientation relative to each other.

As used herein, the term "unitary" refers to a component being created as a single piece or unit. That is, a component that includes multiple pieces that are created separately and then coupled together as a unit is not a "monolithic" component or body. As used herein, a statement that two or more parts or components "engage" one another shall mean that the parts exert a force on one another either directly or through one or more intermediate parts or components. As used herein, the term "number" shall refer to one or an integer greater than one (i.e., a plurality).

Directional phrases used herein, such as, for example, but not limited to, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

Fig. 1 is a schematic diagram of an airway pressure support system 2 according to one specific non-limiting embodiment, wherein the present invention may be implemented in various embodiments thereof. Pressure support system 2 includes a gas flow generator 4, a delivery conduit 6, a patient interface device 8 configured to engage around the airway of a patient, and a headgear 10 for securing patient interface device 8 to the head of a patient (P). The gas flow generator 4 is configured to generate a flow of breathing gas to be delivered to the airway of the patient P by the patient interface device 8. The flow of breathing gas may be heated and/or humidified by a humidifier 12, the humidifier 12 being provided together with the gas flow generator 4 in a common housing 14 (such as shown in dashed lines in fig. 1) or alternatively as a unit separate from the pressure generating device 4 and located outside the pressure generating device 4. As discussed in further detail below, the humidifier 12 is a drip humidifier.

The gas flow generator 4 may include, but is not limited to: ventilators, constant pressure support devices (such as continuous positive airway pressure devices or CPAP devices), variable pressure devices (e.g., manufactured and sold by Philips Respironics of Murrysville, pa., U.S. CPAP)Or C-Flex ^TM A device) and an automatic titration pressure support device. The delivery conduit 6 is configured to communicate a flow of breathing gas from the gas flow generator 4 to the patient interface device 8. The delivery catheter 6 and the patient interface device 8 are often collectively referred to as a patient circuit.

The device is a bi-level device in which the pressure provided to the patient varies with the patient's breathing cycle such that a higher pressure is delivered during inhalation than during exhalation. An auto-titration pressure support system is a system in which the pressure varies with the condition of the patient, such as whether the patient is snoring or experiencing an apnea or hypopnea. The present invention contemplates that gas flow generator 4 is any conventional system for delivering a flow of gas to or for elevating the pressure of gas at the airway of a patient, including the pressure support system and the non-invasive ventilation system outlined above. Although example embodiments utilizing pressurized gas flow are described herein, it should be appreciated that the embodiments of the invention described herein may be readily employed in other applications where pressurization is not typically employed (e.g., without limitation, in high flow therapy applications).

In the exemplary embodiment, patient interface device 8 includes a patient seal assembly 16, which in the illustrated embodiment is a full-face mask. However, it should be appreciated that other types of patient sealing assemblies, such as, but not limited to, nasal/oral masks, nasal cushions, or any other device that facilitates delivery of a flow of breathing gas to the airway of a patient, may be substituted for patient sealing assembly 16 while remaining within the scope of the present invention. It should also be appreciated that the headgear 10 is provided for exemplary purposes only and that any suitable headgear assembly may be employed without departing from the scope of the present invention.

Referring to fig. 2, the drip humidifier 12 includes a water chamber 20, the water chamber 20 being configured to hold a suitable volume of water 22. Water is transferred from the water chamber 20 to a drip nozzle 26 disposed above a heating plate 28 at a predetermined rate by a solenoid-actuated pump (e.g., solenoid pump 24) or other suitable mechanism. The drip nozzle 26 and the heating plate 28 are disposed within the conduit 30, with the conduit 30 extending between a first end 38 (i.e., inlet) and an opposite second end 40 (i.e., outlet). The first end 38 is configured to receive a flow of breathing gas, such as but not limited to from the gas flow generator 4, which is then directed by the conduit 30 (as shown by the box-shaped arrows) to the second end 40 (and further to the patient). The amount of water 22 delivered to the heater plate 28 is a function of the volume of the solenoid pump 24 and the geometry of the drip nozzle 26.

Fig. 3 is a partial schematic cross-sectional view of another airway pressure support system 102 including a humidifier 112 (see also fig. 4) according to one specific non-limiting embodiment of the invention. Airway pressure support system 102 includes similar components to airway pressure support system 2 discussed above and operates similarly to airway pressure support system 2 discussed above. As such, like numerals will be used to designate like parts. Humidifier 112 includes a water chamber 120, a pump 124, a nozzle 126, a heater plate 128, a conduit 130, and separator features (e.g., without limitation, a bag 132). The conduit 130 includes a first end 138, an opposite second end 140, and a wall portion 142, the wall portion 142 defining an interior passageway 144 extending between the first end 138 and the second end 140. The first end 138 is fluidly connected to the gas flow generator 104 and the second end 140 is fluidly connected to the patient interface device 108. Accordingly, it should be appreciated that the internal passageway 144 of the conduit 130 is configured to communicate the flow of breathing gas generated by the gas flow generator 104 between the first end 138 and the second end 140. Further, the wall portion 142 of the catheter 130 includes a generally centrally disposed receiving portion 143, the receiving portion 143 extending through the internal passageway 144 and being positioned generally perpendicular to the longitudinal axis 131 of the catheter 130. As shown, the nozzle 126 extends at least partially through the receiving portion 143.

With continued reference to fig. 3, in one example embodiment, the humidifier 112 further includes a receiving member 134 and a plurality of frame members 170, 171, each coupled to the wall portion 142 of the conduit 130. Receiving member 134 and framing members 170, 171 cooperate to couple heating plate 128 to conduit 130. The pocket 132 is defined by a receiving member 134. The function of the bag 132 will be discussed below, as will the configuration of the receiving member 134 and the frame members 170, 171, as well as the flow path of the water 122.

The receiving member 134 may include an annular body portion 156 and a tongue member 160 extending radially outward from the body portion 156. In addition, the body portion 156 has an interior facing the slotted region 158. As shown in fig. 3, the outer perimeter of the heating plate 128 is positioned in the slotted region 158 and engages the slotted region 158. Receiving member 134 may be made of any material (e.g., without limitation, silicone) configured to maintain the positioning of heating plate 128 without being structurally compromised. The frame members 170, 171, which in the exemplary embodiment are made of a rigid thermoplastic material, may be coupled by any suitable mechanism known in the art (e.g., without limitation, coupled by a snap-fit mechanism, welded together) and preferably form a slotted region 172. Although the disclosed concept is described in connection with two frame members 170, 171, it should be appreciated that a similar suitable alternative humidifier may include one frame member coupled to a receiving member without departing from the scope of the disclosed concept. As shown, tongue member 160 of receiving member 134 is positioned in slotted region 172 to couple receiving member 134 to frame members 170, 171 via a tongue and groove mechanism. However, it should be appreciated that the disclosed concepts contemplate suitable alternative coupling mechanisms.

The nozzle 126 is fluidly connected to the water chamber 120 and is configured to produce water droplets from the water 122 received from the water chamber 120. More specifically, the nozzle 126 has an inlet 150 and an opposite outlet 152, the inlet 150 being fluidly connected to the water chamber 120, and water droplets exiting the nozzle 126 from the outlet 152. The heating plate 128 coupled to the wall portion 142 is positioned to receive water droplets from the nozzle 126. In one example embodiment, the heater plate 128 is positioned directly below the outlet 152 when viewed from the perspective of fig. 3 and 4. In addition, the heating plate 128 is exposed to the internal passages 144. As such, in operation, as water droplets leave the outlet 152 and strike the heater plate 128, the heater plate 128 is configured to evaporate the water droplets and thus humidify the flow of breathing gas flowing from the first end 138 of the conduit 130 to the second end 140 of the conduit 130.

The function of the bag 132 will now be discussed in detail in connection with fig. 3 and 4. As shown, the pocket 132 coupled to the wall portion 142 extends away from the interior passageway 144. In this manner, the bag 132 is configured to shield droplets of water passing from the outlet 152 of the nozzle 126 to the heater plate 128 from the flow of breathing gas. This significantly minimizes the likelihood that water will be undesirably blown into the patient interface device 108. For example, in the event that water undesirably accumulates on the heater plate 128 (e.g., does not evaporate quickly and/or leaves the outlet 152 too quickly), by positioning the outlet 152 in the bag 132 and positioning the heater plate 128 below the outlet 152, water will generally be maintained below and out of the gas flow. As such, the flow of gas will generally not be strong enough to force any accumulated water through the second end 140 of the conduit 130 and into the patient interface device 108. More specifically, the accumulated water (if any) will generally be maintained on the heating plate 128 and/or engaged with the receiving member 134 defining the bag 132. Additionally, in the event of an undesirable tilt condition, wherein airway pressure support system 102 is accidentally tilted such that it rests unevenly on the surface on which it is located, water leaving outlet 152 that does not evaporate immediately will generally be maintained in bag 132.

Fig. 5 is a partial schematic cross-sectional view of another airway pressure support system 202 including a humidifier 212 (see also fig. 6) according to one specific non-limiting embodiment of the invention. Airway pressure support system 202 includes similar components to airway pressure support systems 2 and 102 discussed above and operates similarly to airway pressure support systems 2 and 102 discussed above. As such, like numerals will be used to designate like parts. In addition, only significant differences will be discussed in detail for ease of illustration and economy of disclosure.

As shown in fig. 5 and 6, the separator feature of the humidifier 212 is in the form of a wall portion (e.g., without limitation, a substantially planar member 232) extending radially inward from the wall portion 242 of the conduit 230. In one exemplary embodiment, the planar member 232 and the wall portion 242 form an integral component made from a single piece of material. As shown in fig. 5 and 6, the planar member 232 is positioned between the first end 238 and the heating plate 228. As such, it should be appreciated that the planar member 232 provides substantially the same advantages for the humidifier 212 as the bag 132 provides for the humidifier 112.

More specifically, in operation, the planar member 232 minimizes the likelihood that accumulated water from the water chamber 220 will be blown into the patient interface device 208. Thus, the planar member 232 advantageously prevents the likelihood and/or ensures that the phase change of the water droplet from liquid to vapor will occur without a large likelihood that the water droplet will be entrained by the velocity component of the breathing gas through the second end 240.

As shown in fig. 5, humidifier 212 generally does not have a pouch. The heating plate 228 may be positioned at or above the height of the wall portion 242 (i.e., from the perspective of fig. 5). In the example of fig. 5, the heating plate 228 is generally positioned at the same height as the wall portion 242 of the conduit 230, and the receiving portion 243 is shorter than the receiving portion 143 of the humidifier 112 such that it generally terminates in the internal passageway 244. Accordingly, the outlet 252 of the nozzle 226 is generally positioned in the interior passage 244. Further, the planar member 232 acts as a barrier to the flow of gas from the gas flow generator 204. That is, gas entering first end 238 from gas flow generator 204 will generally not have a direct path over heating plate 228, otherwise it may result in a condition where accumulated water (e.g., water that may not have evaporated fast enough and/or that has accumulated due to exiting nozzle 226 too fast) is undesirably blown past second end 240 and into patient interface device 208. However, the heating plate 228 remains exposed to the internal passage 244 and, as such, serves to evaporate water entering into the internal passage 244, thereby allowing humidified gas to exit the second end 240 and be delivered to the patient interface device 208.

Fig. 7 is a simplified cross-sectional view of a portion of another humidifier 312 according to one specific non-limiting embodiment of the invention. Humidifier 312 is substantially the same as humidifier 212 discussed above. As such, like numerals will be used to designate like parts. In addition, only significant differences will be discussed in detail for ease of illustration and economy of disclosure.

As shown in fig. 7, the wall portion 332 has a generally concave surface 333 that faces the heating plate 328. It should be appreciated that although the wall portion 332 provides substantially the same advantages to the humidifier 312 as the corresponding planar member 232 provides to the humidifier 212, the wall portion 332 provides additional advantages. Specifically, in operation, the concave geometry of the wall portion 332 generally causes the flow of breathing gas through the conduit 330 with relatively little turbulence. That is, the flow of breathing gas will generally be prevented from flowing directly over the heating plate 328 and will do so in such a way that it is smoothly deflected by the wall portion 328.

It should be appreciated that humidifiers 112, 212, and 312 provide different examples of the disclosed concepts. In particular, each of the humidifiers 112, 212, and 312 provides a unique mechanism by which water is prevented from entering the gas stream and blowing into the corresponding patient interface device 108 and 208 (and the patient interface device of the airway pressure support system that includes the humidifier 312). While humidifiers 112, 212 and 312 each accomplish this by means of separator features 132, 232 and 332, it should be appreciated that suitable alternative separator features for minimizing and/or preventing water from entering the gas stream are contemplated herein.

Fig. 8 is a schematic diagram of another airway pressure support system 402 including a humidifier 412, according to one specific non-limiting embodiment, in which the invention may be implemented in various embodiments thereof. Airway pressure support system 402 includes similar components to airway pressure support systems 2, 102, and 202 discussed above (and airway pressure support systems including humidifier 312) and operates similar to airway pressure support systems 2, 102, and 202 discussed above (and airway pressure support systems including humidifier 312). Accordingly, like numerals will be used to designate like parts.

The gas flow generator 404 is configured to pass the flow of breathing gas through the conduit 430 and further to the patient interface device 408. The nozzle 426 is configured to produce water droplets from the water 422 received from the water chamber 420. A heating plate 428 coupled to a wall portion 442 of conduit 430 and exposed to an internal passageway 444 is positioned to receive water droplets from nozzle 426. In this way, humidified breathing gas can be delivered to the patient through the patient interface device 408 as the water droplets evaporate and enter the gas flow.

In accordance with the disclosed concept, the humidifier 412 and thus the airway pressure support system 402 is also configured to minimize the likelihood that dissolved solids (such as, for example, but not limited to, calcium, magnesium, potassium, sodium, chloride, sulfate, and other organic matter) will be passed from the water chamber 420 to the pump 424 and/or be left on the heating plate 428 after water droplets strike the heating plate 428 and evaporate into the internal passageway 444. For example, while humidifiers for airway pressure support systems are often recommended for use with distilled water, users will typically use commercial bottled water or tap water (e.g., from a well or municipal water system) that may contain unwanted contaminants. Although these alternative water types are not recommended for use and generally do not have a detrimental effect on humidifier operation, they can pose problems for long-term use of the pump and generally leave the aforementioned contaminants as residues on the heating plate. If the amount of residue becomes too large, the components of the humidifier will generally have to be replaced. To address these issues, humidifier 412 also includes a filter 433 and optionally a filter meter 447.

Fig. 9-14 show different views of the water chamber 420 and the filter 433. Referring to fig. 12, the water chamber 420 includes a flexible body portion 461, a cover 463, an annular retaining member 465 and a base 467. The body portion 461 of the water chamber 420 includes an inlet 469 and an opposite outlet 471. The cover 463 is selectively coupled to the inlet 469 and has a vent passage 473 defined therethrough. As such, the ventilation passage 473 is configured to allow air to enter the water chamber 420 when the water level therein drops during use. The holding member 465 connects the outlet 471 of the body portion 461 to the base 467. As shown in fig. 12, the base 467 has a body portion 475 that is selectively coupled to the outlet 471 of the body portion 461 of the water chamber 420 and has a channel portion 477 defined therethrough.

The filter 433 has a housing 435, the housing 435 having an inlet 437 and an opposite outlet 439. In addition, the housing 435 of the filter 433 is configured to house a filter medium 441 (partially shown in fig. 12). In one example embodiment, the inlet 437 of the filter 433 is threadably connected to the channel portion 477 of the base 467 and is fluidly connected to the outlet 471 of the body portion 461 of the water chamber 420. In this way, the housing 435 of the filter 433 can be directly coupled to the water chamber 420. However, it should be appreciated that the disclosed concepts contemplate suitable alternative coupling mechanisms (e.g., without limitation, coupling via screws and/or bolts, snaps, and/or quarter-turn features). Additionally, it is contemplated that the water chamber (not shown) may have any suitable alternative number of channels to allow water to drain from the water chamber into the filter. Furthermore, it is within the scope of the disclosed concept that the water chamber be constructed of suitable alternative components and have suitable alternative configurations.

The filter media 441 includes a filter element selected to remove a majority of dissolved solids from the water 422 (fig. 8) as the water passes through the filter 433 thereby preparing the water for boiling. The filter element of filter media 441 may include one or more of the following: coarse stainless steel mesh screens, activated carbon to remove chlorine and bacteria, ion exchange resins to remove many dissolved solids, fibrous webs containing resins, and/or any other suitable components. It is also contemplated that the outlet 439 of the filter 433 may also include a check valve to prevent water from flowing until assembly of the humidifier 412 is complete.

The water chamber 420 also provides improved advantages in portability. More specifically, the water chamber 420 is configured to collapse from a first (expanded) position shown in FIGS. 9-11A to a second (collapsed) position shown in FIGS. 11B, 13 and 14. To do so, the body portion 461 of the water chamber 420 is preferably made of a soft, flexible material such as, for example, but not limited to, silicone. When the water chamber 420 is in the second position (fig. 11B, 13 and 14), the inlet 469 is located internally and is generally concentric with respect to the outlet 471. More specifically, the body portion 461 has a plurality of ridge portions 481, 483, 485. Ridge portion 481 extends from outlet 471, ridge portion 485 extends from inlet 469, and ridge portion 483 extends between ridge portions 481, 485. As best shown in fig. 9-11A, when the water chamber 420 is in the first position, the ridge portions 481, 483, 485 are all in an extended position and are not concentric with respect to each other. As shown in fig. 11B, 13 and 14, when the water chamber 420 is in the second position, the ridge portions 481, 483, 485 are in the collapsed position such that they are all located at approximately the same height (see fig. 11B and 13). In this way, the water chamber 420 is easier to transport than existing water chambers because it can be relatively easily configured so as to be less cumbersome and thus easier to handle and store when not filled with water. In one example embodiment, the water chamber 420 protrudes outward from the housing of the humidifier 412 when in the expanded position and is substantially flush with the top surface of the housing of the humidifier 412 when the water chamber 420 is in the collapsed position.

Referring again to fig. 8, the filter meter 447 has an inlet 449, an outlet 451, a body portion 453 extending between the inlet 449 and the outlet 451, and a mechanism 455 positioned in the body portion 453. Inlet 449 is fluidly connected to outlet 439 of filter 433. The body portion 453 of the filter meter 447 is configured to transfer water from the inlet 449 of the filter meter 447 to the outlet 451 of the filter meter 447. An example configuration of humidifier 412 is provided in which pump 424 is fluidly connected between outlet 471 of water chamber 420 and nozzle 426. In a preferred embodiment, pump 424 is fluidly connected between outlet 451 of filter meter 447 and nozzle 426.

The mechanism 455 of the filter meter 447 is configured to measure the filtration data of the water being conveyed through the body portion 453. In an example embodiment, the mechanism 455 is electrically connected to a processing device (not numbered) of the gas flow generator 404 to communicate the filtered data to the gas flow generator 404. Thus, the filter 433 and the filter meter 447 cooperate to provide a mechanism for the humidifier 412 to remove dissolved solids from the water 422 without the water 422 being distilled.

More specifically, after water 422 has passed through filter media 441 and exited outlet 439 of filter 433, water 422 enters inlet 449 of filter meter 447. In one example embodiment, the filter meter 447 is a total dissolved solids meter having two metal probes (e.g., without limitation, copper probes coated with a material such as gold to minimize corrosion). The probes may be the same size (e.g., without limitation, 1.5 millimeter diameter and about 2 millimeters length exposed to water) and may be placed in parallel at about 5 millimeter center-to-center spacing. Since the mechanism 455 containing the probes is electrically connected to the gas flow generator 404, it should be appreciated that the circuit board of the gas flow generator 404 is configured to measure the electrical conductivity between the two probes. The conductivity measurement may be converted to parts per million (hereinafter "PPM") that provides an indication of the amount of dissolved solids contained in the water passing through the filter meter 447.

In a preferred embodiment, it should be understood that the water passing through filter 433 should have a dissolved solids content of less than 30 PPM. In the event that the dissolved solids measurement by filter meter 447 exceeds 30PPM, the electrical connection between filter meter 447 and gas flow generator 404 will cause gas flow generator 404 to provide an indication to the user that the water quality is too poor (e.g., contains too much dissolved solids) and that the filter needs to be replaced (e.g., a screen reading). Furthermore, it is contemplated that humidifier 412 may not operate to protect pump 424 and heating plate 428 at dissolved solids levels exceeding 30 PPM. Further, humidifier 412 is also configured such that once the dissolved solids content of the water reaches PPM of 20, the user will be notified on gas flow generator 404 that the filter is approaching the end of its lifetime and should be replaced soon.

Once the water 422 has passed through the filter meter 447, the water 422 may flow into the pump 424, and the pump 424 generates pressure that moves the water 422 to the nozzle 426. As previously discussed, the nozzle 426 is configured to generate water droplets from the water 422, and the heating plate 428 is configured to receive water droplets.

Accordingly, it should be appreciated that the airway pressure support system 402 and the humidifier 412 for the airway pressure support system 402 are advantageously configured to operate with any potable water (e.g., tap water, bottled water, distilled water). In particular, distilled water generally does not contain certain problematic dissolved solids that might otherwise damage components of humidifier 412 (e.g., pump 424 and heating plate 428). When tap water and bottled water are used, although the user is not advised to use the humidifier 412, the water will advantageously be filtered by the filter media 441 to remove much of the dissolved solids before exiting the outlet 439. Furthermore, in addition to including filter 433, the failsafe of filter gauge 447 provides an additional advantage of alerting the user to the quality of water exiting outlet 439 of filter 433. That is, although filter 433 is generally configured to remove dissolved solids from water, the use of filter 433 over time may compromise its ability to remove dissolved solids from water. Thus, the filter meter 447 provides a mechanism to address this issue. That is, the mechanism 455 as discussed above is easily configured to alert the user to the quality of water exiting the outlet 439 of the filter 433. If the quality is unsuitable (e.g., greater than 30 PPM), the user may receive an indication on the gas flow generator 404 that the filter media 441 needs to be replaced. Once the filter media 441 has been replaced by a user, non-distilled water (although not preferred) will again be reliably filtered and passed to the pump 424 and heating plate 428 with relatively little dissolved solids therein. In this way, the humidifier 412 is versatile in that it is easily configured to be employed with distilled and non-distilled water without significant problems of damaging the integrity of the operating components (e.g., the pump 424 and the heating plate 428).

Fig. 15 is a schematic diagram of an enlarged portion of another humidifier 512 for an airway pressure support system according to one specific non-limiting embodiment of the invention. Humidifier 512 includes similar components to humidifiers 12, 112, 212, 312 and 412 discussed above, and operates similar to humidifiers 12, 112, 212, 312 and 412 discussed above. Accordingly, like numerals will be used to designate like parts.

The conduit 530 includes a first end 538, a second end 540, and a wall portion 542, the wall portion 542 defining an internal passageway 544 extending between the first end 538 and the second end 540. The nozzle 526 has an outlet 552 configured to produce water droplets from water received from a water chamber (not shown). As shown, the heating plate 528 has a first side 529 facing the nozzle 526 and an opposite second side 531 facing away from the nozzle 526. The first side 529 is positioned to receive water droplets from the nozzle 526. In one example embodiment, humidifier 512 further includes a plurality of heating elements 571, 573 coupled to second side 531 of heating plate 528. The heating elements 571, 573 are configured to heat the heating plate 528 so as to evaporate water droplets striking the first side 529, thereby humidifying the breathing gas.

In addition, the humidifier 512 may also include a thermistor 575 coupled to the second side 531 of the heating plate 528. The thermistor 575 may be positioned closer to the outlet 552 of the nozzle 526 than the heating elements 571, 573 are positioned to the outlet 552 of the nozzle 526. The thermistor 575 may be electrically connected (e.g., via a processing unit) to a gas flow generator of an airway pressure support system that includes the humidifier 512 and allow the processing unit to monitor the temperature of the heating plate 528. In this way, the thermistor 575 provides a mechanism to monitor whether a water droplet exiting the outlet 552 is striking the heating plate 528.

With continued reference to fig. 15, the first and second sides 529, 531 of the heating plate 528 each have a respective central position 533, 535 that is positioned closer to the outlet 552 than any other respective position on the first and second sides 529, 531. The center location 533 may be located directly opposite the center location 535. When viewed from a top plan view (see, e.g., fig. 16), the central locations 533, 535 are positioned directly below the outlet 552. In one example embodiment, the thermistor 575 is positioned at a center location 535 of the second side 531. As shown, the nozzle 526 is positioned generally about a longitudinal axis 527, the longitudinal axis 527 extending through the first and second sides 529, 531, and the longitudinal axis 527 does not pass through the heating elements 571, 573.

Thus, it should be appreciated that the heating plate 528 generally has a centrally located "non-heating zone" without any heating elements as best depicted in FIG. 16. In particular, the innermost border of the heating elements 571, 573 is shown as an outer dashed circle and the space inside thereof is a "non-heating zone". As shown, the heating elements 571, 573 are spaced apart from the central locations 533, 535 by at least a radius R.

With reference to fig. 17, the determination of the spacing of the outlet 552 of the nozzle 526 from the heating plate 528 will now be described in detail. As shown, outlet 552 is positioned at a height H above a central location 533 of first side 529. The inventors have found that when H is less than about 4 millimeters, boiled blisters caused by water droplets striking the heating plate 428 will often bounce and strike the outlet 552, which can cause the nozzle 426 to draw more water from the water chamber than may be desired. Thus, the inventors have found that H is preferably in the range of about 4 millimeters to about X millimeters, where x= (radius R)/tangent (θ).

In the example shown in fig. 17, the humidifier 512 has been tilted to the maximum operating angle θ. The angle θ may correspond to the humidification standard ISO 8185:2007 or any other predetermined maximum judicious operating angle. In one exemplary embodiment, the angle θ is about 20 degrees and the radius R is about 3 millimeters. In other words, the thermistor 575 may be spaced apart from each of the heating elements 571, 573 by at least 3 millimeters. Thus, in one example embodiment, H may be about 6 millimeters. At this level, the water striking the heating plate 528 will generally be far enough away from the outlet 552 that it will not cause the nozzle 526 to accidentally draw more water from the water chamber than necessary. Furthermore, at this height, the water droplets striking the heating plate 528 will generally be close enough that in the event of an unexpected or undesired tilting condition (e.g., up to the maximum operating angle θ), the thermistor 575 will still be able to detect whether the water droplets have struck the heating plate 528.

Fig. 18 is a schematic diagram of a gas flow generator 604 and a humidifier 612 of an airway pressure support system 602 according to one specific non-limiting embodiment of the invention. Similar to the humidifier arrangements previously discussed, the humidifier 612 includes a pump 624 for supplying the water flow 622 from the water chamber 620 to a drip nozzle 626. The drip nozzle 626 is positioned to deliver water droplets to a heating plate 628, the heating plate 628 having a thermistor 675 and heating elements 671, 673 arranged as discussed with respect to the embodiment of fig. 15-17. The pressure support system 602 includes a processing unit 601, which processing unit 601 may be part of a humidifier 612 (as shown), part of a gas flow generator 604, or as a separate element. The processing unit 601 includes a processing portion, which may be, for example, a microprocessor, microcontroller, or some other suitable processing device, and a memory portion, which may be internal to the processing portion or operatively coupled to the processing portion, and which provides a storage medium for data and software executable by the processing portion to control the operation of the gas flow generator 604, the pump 624, and the heating elements 671 and 673, as well as to receive elements from the gas flow generator 604 and inputs from the thermistor 675.

In fig. 19, a flowchart of an example method 700 is shown, the example method 700 may be performed according to one specific non-limiting embodiment of the invention, and the example method 700 may be performed by the processing device 601 upon activation of the humidifier 612. The method 700 begins at 702, where an indication to power the system 602 is received. Typically, such an indication is received from an input device (not shown), such as a power button or other suitable arrangement that may be actuated by the patient, caregiver, or other person initiating the pressure treatment session. After receiving the indication at 702, power is provided to the gas flow generator 604, as shown at 704, such that the gas flow begins through the conduit 630 of the humidifier 612 and onward to the patient. Such flow is allowed to continue for a first predetermined time (in an example embodiment of the invention, the first predetermined time is 10 seconds), as shown at 706, although other time increments may be employed without departing from the scope of the invention.

Next, as shown at 708, the temperature of the heating plate 628 is typically raised from the temperature of the ambient environment to a first predetermined temperature by power supplied to one or more of the heating elements 671 and 673. In an exemplary embodiment of the invention, such first predetermined temperature is about 50 ℃, but other temperatures may be employed without departing from the scope of the invention. As previously discussed with respect to the arrangement of fig. 15-17, the temperature of the heating plate 628 is readily determined by monitoring the resistance of the thermistor 675.

Once the temperature of the heating plate 628 has reached the first predetermined temperature, the temperature is maintained at the first predetermined temperature for a second predetermined period of time, such as shown at 710. In an example embodiment of the invention, such a second predetermined period of time is 10 seconds, but other time increments may be employed without departing from the scope of the invention. Once the second predetermined period of time has elapsed, a countdown timer is started, as shown at 712, that counts down from the predetermined countdown time, and sufficient power is supplied to pump 624 to begin operating pump 624 at the first predetermined duty cycle, such as shown at 714. In an example embodiment of the invention, such a first predetermined duty cycle is a duty cycle of about 20%, but other suitable duty cycles may be employed without departing from the scope of the invention. In an example embodiment of the invention, the countdown timer is set for five minutes, but other time periods may be used without departing from the scope of the invention.

Once pump 624 begins operation at 714, the temperature of heating plate 628 is monitored (via thermistor 675), as shown at 716. Such monitoring continues until a drop in temperature is detected or until the countdown timer reaches zero, as shown in 718 and 720. If the countdown timer reaches zero at 720 before the temperature drop is detected at 718, thus indicating that no water has impacted the heating plate 628 (due to a lack of water in the water chamber 620, a faulty pump, a blockage somewhere between the water chamber 620 and the nozzle 626, or some other problem), then the pump 624 is turned off, as shown at 722, and the heating elements 671 and 673 are turned off, as shown at 724. Optionally, a signal or message may be provided to the patient via any suitable means to indicate that the humidifier has been turned off. Alternatively, if a drop in temperature is detected at 718 before the countdown timer reaches zero, thus indicating that one or more water droplets have impacted the heating plate 628 (i.e., the temperature of the heating plate has dropped slightly due to evaporation of water droplets impacting the plate), then after waiting a third predetermined period of time, such as shown at 726, the duty cycle of the pump 624 is increased to a predetermined second duty cycle at 728. In an example embodiment of the invention, such a second duty cycle is about a 25% duty cycle, but other suitable duty cycles may be employed without departing from the scope of the invention. In an example embodiment of the invention, such a third predetermined period of time is twenty seconds, but other suitable time increments may be employed without departing from the scope of the invention.

After increasing the pump duty cycle at 728, the temperature of the heating plate 628 is increased to about a second predetermined temperature (which coincides with the normal operating temperature), as shown at 730. In an exemplary embodiment of the present invention, such second predetermined temperature is about 120 ℃, but other suitable temperatures may be employed without departing from the scope of the present invention. After reaching the second predetermined temperature, the humidifier continues with normal operation. From the foregoing, it should therefore be appreciated that the method 700 provides an activation mechanism that prevents the heater plate from being fully powered until it is verified that water is being delivered to the heater plate. In addition, by wetting the heating plate at a low temperature, any solids that have previously deposited on the heating plate (from impurities in the water provided in the water chamber) do not decompose and are released into the gas stream. Thus, this approach also reduces/eliminates the release of harmful gases that would otherwise be released from such solids.

FIG. 20 is a schematic cross-sectional view of an example solenoid pump (such as pump 624 of FIG. 18) according to one particular non-limiting embodiment of the invention. The pump 624 includes a housing 680, the housing 680 having an inlet 682 and an outlet 684 defined therein. The pump 624 also includes a deformable diaphragm member 686, the deformable diaphragm member 686 defining a pumping chamber 688 along with a portion of the housing 680. Pumping chamber 688 is separated from inlet 682 via a one-way inlet valve 690, and from outlet 684 via a one-way delivery valve 692, with one-way inlet valve 690 allowing fluid to flow only into pumping chamber 688, and one-way delivery valve 692 allowing fluid to flow only out of pumping chamber 688. The pump 624 also includes a solenoid 694, which when energized by applying power to the terminal T, the solenoid 694 causes the armature 696 to deform the diaphragm member 686 in a manner that reduces the volume of the pumping chamber 688 and thereby forces fluid from the pumping chamber 688 out of the outlet 684 via the delivery valve 692. The pump 624 also includes a spring member 698, the spring member 698 being tensioned to pull the armature 696 back toward the solenoid 694, thereby moving the diaphragm member 686 back into the initial position and increasing the volume of the pumping chamber 688. As the volume of the pumping chamber 688 is increased, fluid is drawn into the pumping chamber 688 via the inlet 682 and the inlet valve 690.

Fig. 21 is an example wiring schematic diagram of an example pump arrangement 800 for powering a pump in a drip humidifier, such as pump 624 of fig. 18 and 20, according to one specific non-limiting embodiment of the invention. The terminal T of the solenoid 694 is selectively powered from a power source 699, the power source 699 being electrically connected to the terminal T via a switch S. The switch S is controlled by a suitable microprocessor, such as the processing unit 601 previously described in connection with fig. 18. By using high frequency Pulse Width Modulation (PWM) of the switch S, power may be supplied to the solenoid 694 according to a desired profile. An example of one such power profile 802 for powering a single actuation of a solenoid pump (such as solenoid 694 of pump 624) according to one specific non-limiting embodiment of the invention is shown in fig. 22.

The power profile 802 extends between a pump volume range 804 and a total extension time 806, the pump volume range 804 corresponding to movement of the armature 696 from a start to a fully extended position, the total extension time 806 being represented in a relative manner (i.e., the time of full extension takes 100% of the extension time) in the example shown in fig. 22. To provide quiet operation of the solenoid, the power profile generally includes: an initial portion 808 that generally increases at a first overall rate; a middle portion 810 that generally increases at a second overall rate that is greater than the first overall rate, and a final portion 812 that decreases at a third overall rate. The initial portion 808 extends from an initial (so) position 814 (i.e., 0) of the armature 696 to a second position 816, the second position 816 being about 20% (i.e., about 20, 20) of both the range 804 and the time 806. The initial portion 808 generally increases at a slow rate near the initial position 814, which then increases near the second position 816. The middle portion 810 generally extends from the second location 816 to a third location 818 (i.e., about 40, 60), the third location 818 being about 40% of the range 804 and 20% of the time 806. The middle portion 810 generally increases at a generally slightly lower rate closer to the second location 816 initially at a greater rate and then closer to the third location 818. The final portion 812 generally extends from the third position 818 to a final substantially fully extended position 820 (i.e., about 100,100), the final substantially fully extended position 820 being about 40% of the range 804 and 60% of the time. The final portion 812 generally decreases at a first rate near the third location 818 and then decreases at a decreasing rate near the final location 820. In an example embodiment of the invention, power is further provided to the solenoid 694 during retraction of the armature 696 in accordance with a mirror image of the power profile 802 (mirrored about a vertical axis passing through 100, 100) to selectively counteract the force applied by the spring 696 in returning the armature 696 back to the initial position 0,0 in a controlled manner. By using such predetermined power profile(s), solenoid 696 operates in a manner that reduces/eliminates potential interference with the user of system 602.

A solenoid driven pump, such as pump 624 of fig. 20, may require a nominal level of power to actuate pump diaphragm 628 and valves 690 and 692, and have sufficient power to overcome the static force to move fluid through the pump. Such a system would require a start-up routine in which more power than the nominal level is required to overcome the initial static condition. If the fluid pump remains idle for an extended period of time, the one-way flow valves (such as 690 and 692) may begin to seize, where the nominal pumping power is insufficient to overcome. One way to overcome this initial stuck condition is to modulate the pump drive energy at or near the resonant frequency of the pump system (+/-about 5%) during the start-up phase. Driving the pump at the resonant frequency provides maximum force for the active check valve and increased power for the passive check valve. In an example embodiment where the power supply of the solenoid actuator is implemented with an H-bridge type power driver, then the polarity of the power to the solenoid can alternate between forward and reverse polarity at the resonant frequency. This approach results in delivering the same power so as not to seize both one-way valves.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" or "comprises" does not exclude the presence of other elements or steps than those listed in a claim. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In any device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain elements are recited in mutually different dependent claims does not indicate that a combination of these elements cannot be used to advantage.

Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.

Claims

1. A method (700) for operating a humidifier (612) coupled to a gas flow generator (604), the humidifier (612) having a pump (624) for providing a supply of water to a heating plate (628), the method comprising:

providing (704) power to the gas flow generator (604);

raising (708) the temperature of the heating plate (628) from ambient temperature to a first predetermined temperature;

-powering (714) the pump (624) with a predetermined first duty cycle;

monitoring (716) the temperature of the heating plate (628) over a duration of time occurring during a predetermined period of time; -increasing (728) the duty cycle of the pump (624) in response to detecting that the temperature of the heating plate falls below the first predetermined temperature before the predetermined period of time expires; and is also provided with

The pump (624) is turned off (722) in response to the predetermined period of time expiring without detecting a drop in temperature.

2. The method of claim 1, further comprising: -waiting (706) for a first predetermined period of time after providing the power to the gas flow generator (604) and before raising the temperature of the heating plate (628) to the first predetermined temperature.

3. The method of claim 2, wherein the first predetermined period of time is 10 seconds.

4. The method of claim 1, wherein the first predetermined temperature is 50 ℃.

5. The method of claim 1, further comprising: an indication to power a pressure support system is received (702) and in response thereto the power is provided to the gas flow generator.

6. The method of claim 1, further comprising: -waiting (710) a second predetermined period of time after raising the temperature of the heating plate (628) to the first predetermined temperature and before powering the pump (624) at the predetermined first duty cycle.

7. The method of claim 1, wherein the predetermined first duty cycle is a 20% duty cycle.

8. The method of claim 1, further comprising: after increasing the duty cycle of the pump (624), the temperature of the heating plate (628) is increased (730) to a second predetermined temperature.

9. A processing unit (601) for use in a pressure support system (602) having a gas flow generator (604) and a humidifier (612) for delivering a humidified gas flow to an airway of a patient, the humidifier (612) having a pump (624) for providing a supply of water to a heating plate (628), the processing unit programmed to:

providing (704) power to the gas flow generator (604);

-powering (714) the pump (624) with a predetermined first duty cycle;

monitoring (716) the temperature of the heating plate (628) over a duration of time occurring during a predetermined period of time;

-increasing (728) the duty cycle of the pump (624) in response to detecting that the temperature of the heating plate falls below the first predetermined temperature before the predetermined period of time expires; and is also provided with

10. The processing unit of claim 9, wherein the processing unit is further programmed to: -waiting (706) for a first predetermined period of time after providing the power to the gas flow generator (604) and before raising the temperature of the heating plate (628) to the first predetermined temperature.

11. The processing unit of claim 9, wherein the first predetermined temperature is 50 ℃.

12. The processing unit of claim 9, wherein the processing unit is further programmed to: an indication to power the system is received (702), and in response thereto, the power is provided to the pressure generating device.

13. The processing unit of claim 9, wherein the processing unit is further programmed to: -waiting (710) a second predetermined period of time after raising the temperature of the heating plate (628) to the first predetermined temperature and before powering the pump (624) at the predetermined first duty cycle.

14. The processing unit of claim 9, wherein the predetermined first duty cycle is a 20% duty cycle.

15. The processing unit of claim 9, wherein the processing unit is further programmed to: after increasing the duty cycle of the pump (624), the temperature of the heating plate (628) is increased (730) to a second predetermined temperature.